Push-pull control



Uni-ted States-Patent O 2,938,404 PUSH-PULL CONTROL David Tatum, Philadelphia, and Fred Machate, Jr., Lansdale, Pa., as'signors to Teleflex Incorporated, North Wales, Pa., a corporation of Delaware Filed Feb. 8, 1957, Ser. No. 639,050 Claims. (Cl. 74- 501) The present invention relates to a novel control structure, and more particularly to a novel flexible push-pull type control device adapted to be operated within a guide conduit.

One important problem encountered in control systems of the type contemplated herein is that of minimizing power losses as the result of frictional contact between the shiftable control element and the guide conduit therefor. For example, a presently commercial available pushpull system now in general use and including two 90 bends has an efiiciency in tension of approximately sixty percent. Various proposals have heretofore been made for reducing frictional losses, but such proposals frequently involve relatively complicated and expensive and therefore uneconomical structures. It is an important object of the present invention to provide a novel push-pull type control device which is of simple and economical construction and which is capable of substantially reducing frictional losses.

A more specific object of the present invention is to provide a novel push-pull type control device including an elongated flexible element of extremely simple construction and roller elements secured thereto in an economical manner and arranged for substantially reducing sliding frictional engagement between the control device and a guide conduit.

Other objects and advantages of the present invention will become apparent from the following description and the accompanying drawings, wherein:

Fig. 1 is a fragmentary elevational view showing a portion of a control system incorporating the features of the present invention;

Fig. 2 is an enlarged partial sectional view taken along line 2-2 in Fig. 1;

Fig. 3 is a cross sectional view taken along line 3-3 in Fig. 2; and

Fig. 4 is a cross sectional view taken along line 4-4 in Fig. 2.

Referring now more specifically to the drawings where-' in like parts are designated by the same numerals throughout the various figures, a control system incorporating features of the present invention includes a guide conduit 12 having a predetermined internal diameter and a push-pull type control device axially shiftable within the guide conduit. In accordance with the present invention, the device 14 comprises an elongated one piece strip 16 formed from resilient flexible material such as spring steel, plastic, or the like. The elongated element 16 is formed so that it is provided with axially short alternate sections 18 and 20 with the sections 18 being disposed in a substantially common plane and the sections 20 being disposed substantially in a common plane and said planes being at right angles to each other. Preferably this structure is accomplished by twisting one pair of immediately adjacent sections 18 and 2.0 in one direction and relatively twisting the next pair of adjacent sections 18 and 20 in the opposite direction.

In order to eliminate sliding frictional contact between the strip 16 and the guide conduit, roller means is carried by each of the sections 18 and 210. As shown best in Figs. 2 and 3, roller means 22 on each section 18 includes a pair of rollers 24 and 26 disposed against opposite sides of the section 18 and connected thereto by a common pin 28. Identicalroller means 3 0 is associated with each'of the sections 20 and includes rollers 32 and 34 connected to the strip section by a pin 36. Each of the rollers has a diameter similar to but slightly less than the internal diameter of the guide conduit so that during operation of the device each roller will engage at one time only'one side of the conduit with rolling contact so as to minimize frictional losses in the system. The rollers, of course, rotate in planes parallel to their associated strip sections so thatsuccessive pairs of 'rollers engage circumferentially offset portions of the guide conduit whereby to maintain the control device generally centrally within the guide conduit throughout its length. It has been found that the control device 16 provides the control system with substantially improved operating efliciencies as compared with standard systems heretofore in general use. For example, efiiciencies in tension of about ninety-one percent have been obtained with the novel control device of the present invention when used in a guide conduit having two bends which relatively high efficiency represents a substantial improvement over the sixty percent efiiciency mentioned above for standard systems.

While the preferred embodiment of the present invention has been shown and described herein, it is obvious that many structural details may be changed without departing from the spirit and scope of the appended claims.

The invention is claimed as follows:

1. A push-pull type control device adapted to operate within guide conduit means of predetermined inside di ameter, comprising an elongated one piece flexible strip having a width less than said diameter and having successive axially short sections disposed in planes arranged at angles to each other, antifriction rollers having a diameter greater than said width and respectively disposed adjacent and substantially parallel to said strip sections and projecting beyond opposite longitudinal edges of their associated strip sections for engaging the guide conduit means when the control device is assembled with the guide conduit means, and a plurality of pin means respectively rotatably connecting said rollers with their associated strip sections.

2. A push-pull type control device adapted to operate within guide conduit means of predetermined inside diameter, comprising an elongated one piece flexible strip having a width less than said diameter and having successive axially short sections twisted with respect to each other and disposed in planes arranged substantially at right angles to each other, rollers having a diameter greater than said width and respectively disposed adjacent and parallel to said sections and projecting beyond longitudinal edges of said sections for engaging guide conduit means when the control device is assembled with the guide conduit means, and a plurality of pin means respectively rotatably connecting said rollers with their associated sections.

3. A push-pull type control device, as defined in claim 2, wherein alternate sections of said strip sections are disposed in common planes, and wherein a first pair of successive sections are twisted in one direction relative to a longitudinal axis of said strip, an immediately adjacent pair of successive sections are relatively twisted in the opposite direction and so on.

4. A push-pull type control device adapted to operate within guide conduit means of predetermined inside diameter, comprising an elongated one piece flexible strip assasos Y having a width less than said diameter and havingsuccesslve axlally short sections disposed in planes arranged at angles to each other, a plurality of pairs of rollers having a diameter greater than said width and respectively associated with said strip sections, the rollers of each of Said pair of rollers being disposed substantially parallel to and atopposite sides of their associated stripfsection and extending laterally beyond a longitudinal edge of their; associated strip section for engaging guide conduit means when the control device is assembled with the guide conduit means, and a plurality of pin means respectively connecting rollers of said pairs of rollers and extending through the strip sections for rotatably connecting the pairs of rollers with their associated strip sections.

5. A push-pull type control device adapted to operate within guide conduit means of predetermined inside diameter, comprising an elongated one-piece flexible strip having a width less than said diameter, said strip including successive axially short substantially straight sections disposed in planes arranged at angles to each other, said strip including axially short twisted portions between and integralljzjtainihglsaid straight sections, antitriction rollers respectively disposed adjacent to and parallel to said straight sections {or engaging guide conduit means when said device is assembled with the guide conduit means, and a plurality of means respectively rotatably connecting said rollers with their associated strip sections.

References Cited in the tile of this patent UNITED STATES PATENTS 1,157,148 Bond Oct. 19, 1915 1,350,986 --Caudron Aug. 24, 1920 1,710,237 Ohlson Apr. 23, 1929 FOREIGN PATENTS 12,705 Great Britain Sept. 3, 1888 of 1888 217,941 Great Britain July 3, 1924 339,108 Great Britain Dec. 4, 1930 118,960 Sweden June 3, 1947 1,979,598

France .a m May 19, 1954 

